1. Field of the Invention
The present invention relates to an interpolating component generator for a scanning line interpolator, and more particularly to an interpolating component generator for a scanning line interpolator utilizing pseudo median filters.
2. Description of the Prior Art
Conventionally, there have been used various scanning line interpolation systems for solving picture quality-deteriorating factors such as line flickers appearing in TV signals of interlaced scan systems, line structure, low vertical resolution. Such scanning line interpolation systems are classified into a line repeat system wherein a previous scanning line component is substituted for a scanning line i.sub.n to be interpolated, as shown in FIG. 1A, an inter-field interpolation system utilizing a line average to use an average between upper and lower scanning line components in the same field as the scanning line i.sub.n to be interpolated, as shown in FIG. 1B, and another inter-field interpolation system wherein a previous scanning line component is substituted for the scanning line i.sub.n to be interpolated, as shown in FIG. 1C.
There have been also used a motion application system wherein motion value of an image is determined so that an intra-field interpolation system is employed for a non-motive region whereas an inter-field interpolation system is employed for a motive region, and a median filter system wherein pixel values around a position to be interpolated are applied to a median filter to calculate a pixel value to be used in interpolation. In particular, U.S. Pat. Nos. 4,967,217 and 4,989,090 issued to Faroudja disclose a scanning line interpolation system wherein two field memories and two line memories are utilized to calculate a pixel value to be used in interpolation. In accordance with this scanning line interpolation system, an output from a temporal median filter is added to a component derived in a field, based on a motion value derived by a motion detector so as to output a final interpolation value. When position of a pixel to be interpolated is i, as shown in FIG. 1D, and a motion coefficient indicative of a motion value is K (0&lt;K&lt;1), the interpolation value can be calculated by the following equation: EQU K * (intra-field component)+(1-K) * median (c,(a+b)/2,d)
wherein, (a+b)/2 is used as the intra-field component.
However, the conventional line repeat system exhibits a considerable deterioration in picture quality such as a step edge phenomenon, even though it is inexpensive. In the scanning interpolation utilizing the line averaging system, a deterioration in picture quality that an image involving a vertical variation becomes dim is generated. On the other hand, the inter-field interpolation system exhibits a good picture quality for non-motive images. In this case, however, a considerable deterioration in picture quality occurs in images involving motions, even though a good picture quality is exhibited for non-motive images.
The median filter system is difficult to be compatible with images involving white noises, due to the characteristic of median filter. Furthermore, the median filter system performs only nonlinear operations, resulting in an increased possibility of an overlap phenomenon. On the other hand, the Faroudja's scanning interpolation system is expensive because of the use of frame memories. Furthermore, this system is difficult to be compatible with images involving diagonal variation because it does not take into consideration diagonal components of images.